CN113251681A

CN113251681A - Refrigeration system with a plurality of heat absorption heat exchangers

Info

Publication number: CN113251681A
Application number: CN202011508864.6A
Authority: CN
Inventors: S·赫尔曼; N·庞迪克卡苏
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2020-02-10
Filing date: 2020-12-18
Publication date: 2021-08-13
Also published as: EP3862657A1; US20210247108A1; US11754320B2

Abstract

A refrigeration system includes a compression device, a heat rejection heat exchanger, an ejector, a first expansion device with a corresponding first heat absorption heat exchanger, and a second expansion device with a corresponding second heat absorption heat exchanger. The ejector has a high pressure inlet, a low pressure inlet and an outlet, and is arranged to receive refrigerant fluid from the heat rejecting heat exchanger at the high pressure inlet. A fluid pathway extends from the outlet of the ejector into the bifurcated flow path to provide separate refrigerant flows from the outlet of the ejector to the first and second expansion devices. The first heat absorption heat exchanger is for providing cooling at a first temperature via a refrigerant fluid, and the refrigerant fluid from an outlet of the first heat absorption heat exchanger is directed to a low pressure inlet of the ejector. The second heat absorption heat exchanger is for providing cooling via the refrigerant fluid at a second temperature lower than the first temperature, and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device.

Description

Refrigeration system with a plurality of heat absorption heat exchangers

Technical Field

The present invention relates to a refrigeration system having a plurality of heat absorption heat exchangers, and a corresponding method for providing refrigeration via a plurality of heat absorption heat exchangers.

Background

As is well known, refrigeration or heating can be provided by a refrigeration system that uses a refrigeration cycle in which a refrigerant fluid is compressed, cooled, expanded, and then heated. In one common use, where such refrigeration systems are used to satisfy cooling loads, cooling of the refrigerant fluid is performed via a heat rejection heat exchanger rejecting heat to the atmosphere, and heating of the refrigerant fluid is performed via a heat absorption heat exchanger absorbing heat from an object to be cooled (such as a refrigerated space for cryogenic storage) or the interior of a building to be occupied by people. In this way, the refrigeration system is able to transfer heat from within the building to the exterior of the building even when the interior is cooler than the atmosphere. A complete or partial phase change of the refrigerant fluid can be used to increase the possible temperature difference between the heat rejection phase and the heat absorption phase.

Disclosure of Invention

Viewed from a first aspect, the present invention provides a refrigeration system comprising: a compression device having an inlet for receiving a refrigerant fluid at a suction pressure and an outlet for providing a compressed refrigerant fluid at a discharge pressure; a heat rejection heat exchanger arranged to receive compressed refrigerant fluid from an outlet of a compression device; an ejector having a high pressure inlet, a low pressure inlet, and an outlet, the ejector arranged to receive refrigerant fluid from the heat rejection heat exchanger at the high pressure inlet of the ejector; a fluid pathway extending from the outlet of the ejector and branching into the branched flow path to provide refrigerant from the outlet of the ejector to the first expansion device and the second expansion device; a first heat absorption heat exchanger arranged to receive refrigerant fluid from a first expansion device; and a second heat absorption heat exchanger arranged to receive refrigerant fluid from the second expansion device; wherein the first heat absorption heat exchanger is for providing cooling via a refrigerant fluid at a first temperature and the refrigerant fluid from the outlet of the first heat absorption heat exchanger is directed to the low pressure inlet of the ejector; wherein the second heat absorption heat exchanger is for providing cooling via the refrigerant fluid at the second temperature, and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device; and wherein the second temperature is lower than the first temperature.

With this arrangement it is possible to provide cooling at two different temperatures when only a single compression device and a single ejector are used. The connection of the first heat absorption heat exchanger between the outlet of the ejector and the low pressure inlet of the ejector allows it to provide a sub-circuit with respect to the first heat absorption heat exchanger, while the second heat absorption heat exchanger is placed on the main circuit, wherein the outlet of the second heat absorption heat exchanger directs the refrigerant towards the suction inlet of the compression device. The second heat absorption heat exchanger may be operated at the suction pressure of the compression device (i.e. the lowest pressure within the circuit), while the first heat absorption heat exchanger may be operated at a higher pressure as provided by the suction pressure at the low pressure inlet of the ejector.

Advantageously, the first heat absorption heat exchanger may be used for air conditioning and may thus be operated at a refrigerant fluid temperature in the range of 0 ℃ to 25 ℃ and/or may be arranged for an air side temperature in the range of 15 ℃ to 30 ℃, such as for cooling air at 5 ℃, e.g. from 25 ℃ to 20 ℃, while the second heat absorption heat exchanger may be used for medium temperature applications (such as for refrigeration cabinets) and may thus be operated at a refrigerant fluid temperature in the range of-35 ℃ to 0 ℃ and/or may be arranged for an air side temperature in the range of-25 ℃ to 8 ℃, such as for cooling cabinets to an internal temperature in the range of 0 ℃ to 8 ℃ for refrigerated storage or-25 ℃ to-10 ℃ for frozen storage. Other possible medium temperature applications include chilled water, in which case the first heat absorption heat exchanger is a plate or shell/tube heat exchanger that cools the water. Thus, the refrigeration system may conveniently provide cooling for facilities that require a combination of such heat exchangers, such as buildings that require both air conditioning and refrigerated storage with relatively low capacities involved. This typically occurs in the case of small retail establishments, such as gas stations or small stores that require air conditioning and refrigeration for refrigerated goods and/or perishable goods.

The first and second expansion devices may provide different degrees of expansion to provide a desired difference in refrigerant temperature at the first and second heat absorption heat exchangers. The first expansion device and/or the second expansion device may for example be electronic expansion devices with a controllable degree of expansion. This allows control of the expansion device(s) so as to vary the cooling provided by the first and/or second heat absorption heat exchangers.

The ejector is used to allow an additional circuit comprising a first heat absorption heat exchanger, and the ejector provides two suction pressures via a high pressure inlet and a low pressure inlet, wherein the combined flow exits at the outlet. The ejector advantageously receives via the high pressure inlet all refrigerant fluid flowing through the heat rejecting heat exchanger and some or all of the refrigerant fluid that has subsequently passed through the first heat accepting heat exchanger. The ejector may be, for example, a low entrainment/high lift modulating ejector. Such an ejector may be arranged to modulate the Kv value over the motive nozzle throat diameter (otherwise known as the motive nozzle throat diameter) by means of a modulation means (e.g. an axially adjustable needle or similar method of adjustable orifice flow area) and may be made to perform at the total motive (high side) mass flow rate, but only part of the mass flow rate is drawn at the low pressure suction inlet, typically referred to as the low entrainment/high lift method. The ejector may be arranged to provide an ejector lift force between 0 and 15 bar depending on the application and conditions. The refrigeration system may comprise only a single ejector device, i.e. there may be only one ejector stage as specified above with inlet connections to the heat rejecting heat exchanger and the first heat absorbing heat exchanger and outlet connections transferring fluid towards the branched flow paths. Thus, the refrigeration system advantageously does not comprise any further ejector devices located at other positions within the refrigerant circuit. However, in some embodiments, a single ejector device may comprise a multi-bank ejector.

The refrigeration system may include a receiver with an inlet to receive refrigerant fluid from the outlet of the ejector and a liquid outlet to provide refrigerant fluid to the branched flow path. Thus, the first expansion device and the second expansion device may be provided with refrigerant fluid from the liquid outlet of the receiver. This is beneficial because the ejector outlet typically has a two-phase flow, with the result that expansion is difficult to control. The receiver enables the expansion device to be provided with a single phase liquid refrigerant fluid, allowing the expansion to be more consistent and/or more easily controlled. The gas outlet of the receiver may be in communication with the inlet of the compression device. For example, as discussed below, this may be via an expansion valve, or the compression device may comprise a medium pressure inlet.

The compression means may be a compressor of any suitable form. Optionally, the compression device may provide two compression stages, for example wherein the outlet of the second heat absorption heat exchanger provides refrigerant fluid to the suction inlet of the first compression stage; and a discharge outlet of the second compression stage provides compressed refrigerant fluid to the heat rejection heat exchanger. The compression device may use an arrangement of a plurality of compressor elements to provide two-stage compression with a medium pressure inlet (and optionally a medium pressure outlet) as discussed above. For example, there may be multiple compressor elements driven by the same compressor motor. The refrigeration system may include a single compression device, such as a two-stage device as discussed herein. Optionally, the refrigeration system does not use compressors in parallel. The refrigeration system may be devoid of any additional compression device located between the heat rejection heat exchanger and the ejector and/or devoid of any additional compression device located between the ejector and the heat absorption heat exchanger. Thus, the proposed system may not rely on multiple compression devices to achieve multiple different endothermic pressures, but only utilize an ejector for allowing the different endothermic pressures.

The compression device may comprise a medium pressure inlet. In one arrangement, as mentioned above, the medium pressure inlet may be connected to the gas outlet of the receiver. Alternatively or additionally, the intermediate pressure inlet may be used for an intercooler. In this case, the compression device may have a medium pressure outlet for directing refrigerant fluid to the intercooler, and refrigerant fluid from the outlet of the intercooler may be directed to the medium pressure inlet, optionally in combination with refrigerant fluid flowing from the gas outlet of the receiver. The intercooler may include an intercooler heat rejection heat exchanger in combination with a heat rejection heat exchanger receiving compressed refrigerant from an outlet of the compression device.

The heat rejecting heat exchanger may be a condenser for at least partially condensing compressed refrigerant fluid from the compression device, whereby the refrigerant fluid is a liquid at the outlet of the heat rejecting heat exchanger. The condenser and intercooler as discussed above may be combined together so that heat is rejected to the air in the air flow path, passing through the intercooler and then through the condenser in sequence. The intercooler and/or condenser may be provided with suitable heat transfer elements, such as fins or the like, on the exterior thereof. The heat rejecting heat exchanger may be a gas cooler unit, e.g. a gas cooler for carbon dioxide refrigerant. Thus, the refrigeration system may use carbon dioxide as the refrigerant fluid. Alternatively, the refrigeration system may use a high pressure refrigerant other than carbon dioxide, such as, for example, R410A.

In a simple configuration of the refrigeration system, the outlet of the first heat absorption heat exchanger is directly coupled to the low pressure inlet of the ejector without any intervening components. However, it has been found that the operating range of the system can be increased if additional features are provided to allow for improved control of the flow of refrigerant fluid to the ejector. In one possible arrangement, a non-return valve is provided between the outlet of the first heat absorption heat exchanger and the low pressure inlet of the ejector to prevent flow reversal of fluid flow away from the ejector under some operating conditions. Additionally or alternatively, a bypass line may be provided to allow refrigerant fluid flow from the outlet of the first heat absorption heat exchanger to the inlet of the compression device. The bypass line may comprise a bypass valve for controlling the flow of refrigerant fluid along the bypass line and/or for controlling the pressure at the outlet of the first heat absorption heat exchanger. In the presence of the bypass line, the refrigeration system may be arranged for a first mode of operation in which the bypass valve is closed and all refrigerant fluid from the first heat absorption heat exchanger flows to the ejector low pressure inlet, and a second mode of operation in which the bypass valve is open or partially open and at least some of the refrigerant fluid from the first heat absorption heat exchanger flows through the bypass line.

Optionally, the refrigeration system comprises one or more internal heat exchangers for heat transfer between refrigerant fluids at different temperatures within the refrigeration system. Thus, there may be at least one internal heat exchanger for heat transfer from a first point in the system to a second point in the system.

For example, the first point may be located after the ejector outlet and before the expansion device, optionally before the branched flow path, wherein the second point is located after the second heat absorption heat exchanger and before the inlet of the compression device. In this case, the first point may also be located after the receptacle, wherein the receptacle is connected as above, i.e. the first point may be located after the liquid outlet of the receptacle. Thus, the internal heat exchanger can transfer heat between the liquid refrigerant after the receiver and the gaseous (or two-phase) refrigerant after the second heat absorption heat exchanger.

Alternatively or additionally, the first point may be located after the outlet of the heat rejecting heat exchanger and before the high pressure inlet of the ejector, wherein the second point is located between the gas outlet of the receiver and the inlet to the compression device, such as between the gas outlet of the receiver and the medium pressure inlet of the compression device discussed above. The internal heat exchanger may thus transfer heat between the refrigerant fluid after the heat rejecting heat exchanger and the gaseous refrigerant after the receiver gas outlet.

Both of the internal heat exchangers discussed above may be present in conjunction with the receiver such that there is a first internal heat exchanger transferring heat from the refrigerant liquid located after the liquid outlet of the receiver to the refrigerant fluid located after the second heat accepting heat exchanger and a second internal heat exchanger transferring heat from the refrigerant fluid located after the heat rejecting heat exchanger to the refrigerant gas located after the gas outlet of the receiver.

The internal heat exchanger may be a plate type heat exchanger, such as a brazed plate type heat exchanger, with counter-flow or cross-flow (or cross-flow) of refrigerant fluid from the first point and the second point.

Optionally, the refrigeration system may include a heat recovery device located after the compression device and before the heat rejection heat exchanger. Thus, there may be a suitable valve arrangement (such as a three-way valve) as follows: for allowing some or all of the compressed refrigerant to pass through the coil for heat recovery before the heat rejecting heat exchanger.

The first and/or second heat absorption heat exchanger with the refrigerant fluid at the respective first and second temperature may optionally be provided in parallel with a further heat absorption heat exchanger with the refrigerant fluid at the respective first or second temperature. Thus, the refrigeration system may be arranged for heat absorption via a refrigerant fluid at a first temperature using two or more heat absorption heat exchangers in parallel, such as a plurality of air conditioning evaporators in the exemplary embodiment, preferably with a corresponding plurality of expansion valves. Alternatively or additionally, the refrigeration system may be arranged for heat absorption via the refrigerant fluid at the second temperature using two or more heat absorption heat exchangers in parallel, such as a plurality of medium temperature evaporators in the exemplary embodiment, preferably with a corresponding plurality of expansion valves.

The refrigeration system may include a controller for controlling one or more elements of the system (such as for controlling some or all of the compression device, the first expansion device, and the second expansion device). Where there are optional features such as bypass lines and/or heat recovery devices, then, the controller may be used to control the respective valves in order to control the operation of the bypass and/or heat recovery.

The refrigeration system may be a rack type refrigeration system (rack type refration system) and, thus, may include a rack mounted compressor. Alternatively, the refrigeration system may be a Cooling Distribution Unit (CDU) type refrigeration system. As noted above, the refrigeration system may use carbon dioxide refrigerant fluid, and this may be done in the context of a rack system or CDU system.

The refrigeration system may be provided as part of a facility for providing a combination of air conditioning and moderate cooling, and the invention thus extends to a facility for providing air conditioning and moderate cooling comprising a refrigeration system as discussed hereinabove. The facility may be a facility for a small retail establishment as discussed above, such as a gas station or small store.

Viewed from a further aspect the present invention provides a method for refrigeration with cooling at two temperatures, the method comprising providing a refrigeration system as set out hereinabove, such as in the first aspect and optionally including further features as discussed hereinabove; providing a first refrigeration temperature using a first heat absorption heat exchanger; and using the second heat absorption heat exchanger to provide a second refrigeration temperature.

The method may comprise cooling air using the first heat absorption heat exchanger for air conditioning and/or cooling air using the second heat absorption heat exchanger for refrigerating or freezing the stored goods.

Drawings

Certain exemplary embodiments of the invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

fig. 1 shows a refrigeration system having two heat absorption heat exchangers;

FIG. 2 illustrates another refrigeration system using two heat absorption heat exchangers; and

figure 3 shows a further refrigeration system using a plurality of heat absorption heat exchangers together with an internal heat exchanger.

Detailed Description

A simple refrigeration system is shown schematically in fig. 1 to illustrate the basic principle of using an ejector to provide a multiple temperature arrangement. The refrigeration system includes a compression device 12, a heat rejecting heat exchanger 14, an ejector 20, a first expansion device 18, a first heat accepting heat exchanger 16, a second expansion device 22, and a second heat accepting heat exchanger 24. The refrigeration system may use carbon dioxide refrigerant. The refrigeration system contains a refrigerant fluid and the circulation of the refrigerant fluid through the compression device 12 enables the refrigeration system to utilize the refrigeration cycle to meet two types of cooling loads via two different temperatures at the first heat absorption heat exchanger 16 and the second heat absorption heat exchanger 24.

The first heat absorption heat exchanger 16 may for example be used for air conditioning and may therefore operate with a refrigerant fluid temperature in the range 0 ℃ to 25 ℃. The second heat absorption heat exchanger 24 provides cooling for lower temperatures (such as for refrigerated or frozen storage of goods) and may therefore operate with refrigerant fluid temperatures in the range-35 ℃ to 0 ℃. The higher pressure inlet of the ejector 20 receives refrigerant fluid from the outlet of the heat rejecting heat exchanger 14 and the lower pressure inlet of the ejector 20 receives refrigerant fluid from the outlet of the first heat absorbing heat exchanger 16. It will be appreciated that the arrangement of the ejector 20 allows for two different temperatures at the two heat

absorption heat exchangers

16, 24, since the pressure at the lower pressure inlet of the ejector 20 may be different from the suction pressure for the compression device 12.

Broadly, the operation of the various portions of the refrigeration system is as follows. The compression device 12 has an inlet for receiving a refrigerant fluid at a suction pressure and an outlet for providing a compressed refrigerant fluid at a discharge pressure. The heat rejecting heat exchanger 14 is arranged to receive compressed refrigerant fluid from an outlet of the compression device 12, and an outlet of the heat rejecting heat exchanger 14 is connected to a high pressure inlet of the ejector 20. The ejector further has: a low pressure inlet, as noted elsewhere herein, that receives fluid from the first heat absorption heat exchanger 16; and an outlet from which refrigerant fluid is directed toward the

expansion devices

18, 22. The refrigerant fluid reaches the expansion device via a fluid pathway that extends from the outlet of the ejector 20 and branches into a branched flow path to provide refrigerant from the outlet of the ejector 20, with the separated flows directed to the first and

second expansion devices

18, 22.

The first heat absorption heat exchanger 16 is arranged to receive refrigerant fluid from the first expansion device 18, and the second heat absorption heat exchanger 24 is arranged to receive refrigerant fluid from the second expansion device 22. The

expansion devices

18, 22 are capable of providing different degrees of expansion so that the first heat absorption heat exchanger 16 will provide cooling via the refrigerant fluid at a first temperature and the second heat absorption heat exchanger 24 will provide cooling at a second, lower temperature. Following the absorption of heat at the first heat absorption heat exchanger 16, thereby providing cooling (such as for air conditioning), the refrigerant fluid from the outlet of the first heat absorption heat exchanger 16 is directed to the low pressure inlet of the ejector 20. After the other refrigerant fluid stream passes through the second heat absorption heat exchanger 24, thereby providing lower temperature cooling (such as for refrigerated or frozen storage of goods), the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device.

By way of example, the heat rejection heat exchanger 14 may be a gas cooler unit for cooling of compressed carbon dioxide refrigerant. The heat rejecting heat exchanger 14 may be a condenser for at least partially condensing a refrigerant fluid. The first and

second expansion devices

18, 22 are

electronic expansion valves

18, 22 for expanding the refrigerant fluid at a controlled degree of expansion, and the first and second heat

absorption heat exchangers

16, 24 are evaporators for at least partially evaporating the refrigerant fluid. The refrigeration system may be arranged such that the refrigerant fluid is fully condensed at the condenser 14 and fully evaporated at the

evaporators

16, 24. The compression device 12 is used for compression of a refrigerant fluid and for circulation of the refrigerant fluid around the refrigeration system.

The refrigeration circuit is controlled by a controller 26, and controller 26 may, for example,

control expansion devices

18, 22 and compressor 12. Control of the refrigeration circuit may be made with reference to various inputs to controller 26, such as user inputs as well as external temperature and/or temperature measurements and/or pressure measurements associated with the refrigeration circuit, and so forth. The controller 26 in this example is capable of controlling the

expansion devices

18, 22 to match the refrigeration system to varying cooling loads at the first evaporator 16 and the second evaporator 24.

Fig. 2 shows a refrigeration system utilizing an ejector 20 in a manner similar to the arrangement of fig. 1, with the addition of a receiver 28, and also with the addition of an intercooler 30, along with the use of a compression device 12 with a medium pressure inlet, such as a suitable two-stage compression device 12. Although the system of fig. 1 is well used to explain the basic principles of the proposed arrangement, it is in practice difficult to control when there is a two-phase flow at the

expansion devices

18, 22. The additional optional feature of fig. 2 allows for easier control of the system, which therefore has the ability to achieve a high level of efficiency. Improvements in the control of the system of fig. 1 may alternatively be provided by other optional features, while still retaining the single stage compressor, such as via the addition of a receiver 28 similar to that of fig. 2 (wherein the gas outlet of the receiver is connected to the suction inlet of the single stage compressor via a suitable valve). Those skilled in the art will appreciate that other variations are possible.

In the case of the arrangement of fig. 2, the inlet of the receiver 28 receives refrigerant fluid, which may be a two-phase mixture, from the outlet of the ejector 20. The receiver separates the refrigerant fluid into liquid and gaseous refrigerant. The liquid outlet of the receiver 28 provides refrigerant fluid (liquid) to the branched fluid pathway and, as such, the

expansion devices

18, 22 will receive liquid refrigerant. The heat absorption by the first heat absorption heat exchanger 16 and the second heat absorption heat exchanger 24 then proceeds as described above. The gas outlet of receiver 28 is connected to an intercooler circuit with intercooler 30, and refrigerant fluid from the gas outlet of receiver 28 is directed to the intermediate pressure inlet of two-stage compression device 12. The two-stage compression device 12 includes a high pressure stage 12a that takes refrigerant fluid from a medium pressure inlet and compresses the refrigerant fluid to a discharge pressure ready to be directed toward the heat rejecting heat exchanger 14. There is also a low pressure stage 12b, the low pressure stage 12b receiving refrigerant fluid at suction pressure from the second heat accepting heat exchanger and compressing the refrigerant fluid to an intermediate pressure. The intermediate pressure refrigerant fluid passes from the outlet of the low pressure stage 12b through the intercooler 30 and is fluidly combined with the refrigerant from the gas outlet of the receiver 28 before being directed to the inlet of the high pressure stage 12 a.

This arrangement allows better handling of the two-phase refrigerant from the outlet of the ejector 20 and also adds further cooling of the refrigerant via the intercooler 30. An intercooler 30 can advantageously be used in series with the heat rejection heat exchanger 14, which may be a gas cooler unit, such as a carbon dioxide gas cooler for use with a carbon dioxide refrigerant fluid. Other features of fig. 2 not mentioned in detail may be similar to those discussed above with respect to fig. 1.

Possible additional features of more complex multi-temperature arrangements are shown in the refrigeration system of fig. 3. The refrigeration system of fig. 3 includes additional elements that can allow for an increased operating range for the system and a greater degree of control when varying cooling capacities at the first and second temperatures are desired. The arrangement of fig. 3 has the added feature of disposition with respect to the refrigerant fluid from the outlet of the first heat absorption heat exchanger, in particular, a non-return valve 32 is provided between the outlet of the first heat absorption heat exchanger 16 and the low pressure inlet of the ejector 20, in order to prevent flow reversal in the event that fluid flows away from the ejector 20. Additionally, a bypass line 34 may be provided for allowing refrigerant fluid flow from the outlet of the first heat absorption heat exchanger 16 to the suction inlet of the compression device 12. The bypass line 34 may comprise a bypass valve 36 for controlling the flow of refrigerant fluid along the bypass line 34 and thus for controlling the pressure at the first heat absorption heat exchanger 16.

The refrigeration system of fig. 3 also includes one or more

internal heat exchangers

38, 40 for transferring heat between refrigerant fluids at different temperatures within the refrigeration system. These

internal heat exchangers

38, 40 may be brazed plate heat exchangers.

The first internal heat exchanger 38 provides for heat transfer from the first flow path after the receiver 28 to the second flow path in the system after the second heat absorption heat exchanger 24. As seen in fig. 3, the first flow path of the first internal heat exchanger 38 is located between the receiver 28 and the branch point of the flow path to the

expansion devices

18, 22. The second flow path of the first internal heat exchanger 38 is located after the second heat absorption heat exchanger 24 and before the inlet of the compression device 12. The first internal heat exchanger thus transfers heat between the liquid refrigerant after the receiver 28 and the gaseous (or two-phase) refrigerant after the second heat absorption heat exchanger 24.

The second internal heat exchanger 40 provides for heat transfer from a first flow path located after the outlet of the heat rejecting heat exchanger 14 and before the high pressure inlet of the ejector 20 and a second flow path located between the gas outlet of the receiver 28 and the intermediate pressure inlet to the compression device 12. The second internal heat exchanger 40 thus transfers heat between the refrigerant fluid after the heat rejecting heat exchanger 14 and the refrigerant after the gas outlet of the receiver 28.

Additional optional features may also be present, as illustrated by the dashed line features in fig. 3. For example, the refrigeration system can include a heat recovery device located after the compression device 12 and before the heat rejection heat exchanger 14. Thus, there may be a three-way valve 42 for allowing some or all of the compressed refrigerant to pass through a coil 44 for heat recovery before the heat rejecting heat exchanger 14. A third internal heat exchanger 46 can be included in the heat recovery system for exchanging heat between the cold and hot circuits to the coil 44. Alternatively or additionally, the first heat absorption heat exchanger 16 and/or the second heat absorption heat exchanger 24 can be connected in parallel with further heat absorption heat exchangers 16 ', 24', which further heat absorption heat exchangers 16 ', 24' thus also handle the refrigerant fluid at the respective first or second temperature. Thus, the refrigeration system can be arranged for heat absorption via a refrigerant fluid at a first temperature using two or more heat absorption heat exchangers 16, 16 'in parallel with a corresponding plurality of expansion valves 18, 18'. For example, there may be a plurality of air conditioning evaporators. Similarly, the refrigeration system can include two or more heat absorption heat exchangers 24, 24' in parallel with refrigerant at a second, lower temperature, such as a plurality of medium temperature evaporators for refrigeration or freezing of stored goods. Again, this may be achieved using a corresponding plurality of expansion valves 22, 22'.

The refrigeration system of fig. 3 can include: a controller (not shown) for control of the two-stage compressor 12 in a manner similar to that described above;

expansion devices

18, 22, and further expansion devices 18 ', 22' (when present); and various valves (when present), such as the bypass valve 36 and/or the three-way valve 42.

Each of the various refrigeration systems described above uses the ejector 20 in a similar manner when in use, so as to allow two different pressures and therefore two different cooling temperatures for the heat

absorption heat exchangers

16, 24.

Claims

1. A refrigeration system comprising:

a compression device having an inlet for receiving a refrigerant fluid at a suction pressure and an outlet for providing a compressed refrigerant fluid at a discharge pressure;

a heat rejection heat exchanger arranged to receive compressed refrigerant fluid from the outlet of the compression device;

an ejector having a high pressure inlet, a low pressure inlet, and an outlet, the ejector arranged to receive refrigerant fluid from the heat rejection heat exchanger at the high pressure inlet of the ejector;

a fluid pathway extending from the outlet of the ejector and branching into a branched flow path to provide refrigerant from the outlet of the ejector to first and second expansion devices;

a first heat absorption heat exchanger arranged to receive refrigerant fluid from the first expansion device; and

a second heat absorption heat exchanger arranged to receive refrigerant fluid from the second expansion device;

wherein the first heat absorption heat exchanger is for providing cooling via refrigerant fluid at a first temperature and refrigerant fluid from the outlet of the first heat absorption heat exchanger is directed to the low pressure inlet of the ejector;

wherein the second heat absorption heat exchanger is for providing cooling via a refrigerant fluid at a second temperature and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device; and

wherein the second temperature is lower than the first temperature.

2. A refrigeration system according to claim 1, wherein the first heat absorption heat exchanger is used for air conditioning and for operation with an air side temperature in the range of 15 ℃ to 30 ℃, while the second heat absorption heat exchanger is used for medium temperature applications and for operation with an air side temperature in the range of-25 ℃ to 8 ℃.

3. A refrigeration system according to claim 1 or 2, wherein the first and second expansion devices are arranged to provide different degrees of expansion.

4. A refrigeration system according to claim 1, 2 or 3, wherein the ejector high pressure inlet receives all of the refrigerant fluid flowing through the heat rejection heat exchanger.

5. A refrigeration system according to any preceding claim, comprising a receiver with an inlet to receive refrigerant fluid from the outlet of the ejector and a liquid outlet to provide refrigerant fluid to the branched flow path.

6. The refrigeration system of claim 5, wherein the gas outlet of the receiver is in communication with the intermediate pressure inlet of the compression device.

7. A refrigeration system according to any preceding claim, wherein the compression device has two compression stages, with the outlet of the second heat absorption heat exchanger providing refrigerant fluid to a suction inlet of a first compression stage and a discharge outlet of a second compression stage providing the compressed refrigerant fluid to the heat rejection heat exchanger.

8. The refrigeration system of claim 7, comprising an intercooler, wherein the compression device includes a medium pressure outlet for directing refrigerant fluid to the intercooler, and wherein the refrigerant fluid from the outlet of the intercooler is directed to the medium pressure inlet of the compression device.

9. A refrigeration system according to any preceding claim, without any further compression device located between the heat rejecting heat exchanger and the ejector and/or without any further compression device located between the ejector and the heat absorbing heat exchanger.

10. A refrigeration system according to any preceding claim, wherein the heat rejection heat exchanger is a gas cooler unit.

11. The refrigeration system of any preceding claim, wherein the refrigeration system is configured for use with carbon dioxide refrigerant.

12. A refrigeration system according to any preceding claim, comprising a non-return valve between the outlet of the first heat absorption heat exchanger and the low pressure inlet of the ejector so as to prevent flow reversal if fluid flows away from the ejector.

13. A refrigeration system according to any preceding claim, comprising a bypass line to allow refrigerant fluid flow from the outlet of the first heat absorption heat exchanger to the inlet of the compression device, wherein the bypass line comprises a bypass valve for controlling the flow of refrigerant fluid along the bypass line and/or for controlling the pressure at the outlet of the first heat absorption heat exchanger.

14. A refrigeration system according to any preceding claim, comprising one or more internal heat exchangers for heat transfer between refrigerant fluids at different temperatures within the refrigeration system.

15. A method for refrigeration with cooling at two temperatures, the method comprising: providing a refrigeration system according to any preceding claim; using the first heat absorption heat exchanger to provide a first refrigeration temperature; and using the second heat absorption heat exchanger to provide a second refrigeration temperature.